Russia's Lukoil and other buyers are in talks with Regal Petroleum about purchasing its gas fields in Ukraine five months after a similar deal with Shell fell apart.

Regal, an exploration and development company with a chequered history, said it had received preliminary approaches about "possible transactions", but stressed that talks were at an early stage.

Shares in Regal, which fell 5.5% on Monday moved cautiously ahead 1% to 165p as the new management led by chairman and chief executive, David Greer, confirmed it was in talks with unnamed buyers. Lukoil was not named by Regal, but industry sources confirmed that the Russian company could pay as much as $1bn (£500m) to increase its reserves in Ukraine.

Regal controls Ukraine's Mekhediviska-Golotvschinska and Svyrydivske fields which are together estimated to hold 169m barrels of oil and whose small production levels could be ramped up to 50,000 barrels a day in the medium-term. In November the company announced that it had tied up a sales agreement with Shell only for it to be scrapped two days later.

Greer, a former Shell executive, joined at the same time, replacing Regal's then chairman Francesco Scolari and chief executive Neil Ritson, the architect of the original sales agreement with Shell.

Regal has been synonymous with turbulence and, in January, it was referred to the London Stock Exchange disciplinary committee after allegedly breaking the rules over the disclosure of price sensitive information. The move hails back to 2003 when Regal announced that a much-hyped well in the Adriatic Sea had produced more water than oil.